Scab (Venturia inaequalis) is a very serious disease for apples causing up to 80% of loss in yield but there are only a few studies on postharvest quality of scab-resistant cultivars. In this study we evaluated the effect of 1-methylcyclopropene (1-MCP) on fruit quality, total phenolic content, and antioxidant capacity after storage of four scab-resistant cultivars and compared to a standard cultivar, "Golden Delicious." In general, ethylene production and respiration rates significantly differed among cultivars, between control and 1-MCP-treated fruits, and between storage duration regimes. 1-MCP treatment retarded fruit softening and lowered juice pH but storage effect on soluble solids and acidity depended on cultivar and 1-MCP treatment. Total phenolic content was significantly affected by storage duration and 1-MCP treatment. Antioxidant capacity of the four scab-resistant cultivars was either similar to or significantly higher than that of "Golden Delicious" with the 1-MCP-treated fruits having significantly higher antioxidant capacity than the nontreated fruits after storage. Our results clearly show that the quality of four scab-resistant cultivars was comparable to that of "Golden Delicious" and 1-MCP effect differed among cultivars. These differences need to be considered in developing storage regime to minimize quality deterioration during long-term storage.
IntroductionThe hazardous effects of pesticides on human health and the environment have contributed to the introduction of cultivars with effective resistance genes to major plant diseases. Yield losses from fungal diseases are significant in most apple producing countries worldwide. Apple scab, caused by the fungus Venturia inaequalis, is one of the most destructive diseases of apples throughout the world, causing up to 80% loss in yield without chemical intervention, which could include multiple classes of fungicides applied up to 22 times during the growing season [1]. In 1944 Hough, from University of Illinois, was the first to identify the scab-resistant gene in Malus floribunda [2]. Since 1944, additional scab-resistant genes have been identified in other apple species [3]. In 1948, three US universities (Purdue, Rutgers, and Illinois, PRI) formed a research team to develop apple cultivars resistant to scab, utilizing the gene [3]. In recent years, several apple cultivars containing have been introduced into commercial production from the PRI program, including "Dayton," "Prima," "Priscilla," and "Jonafree" [4]. Among the most promising introductions are "WineCrisp" [5], "CrimsonCrisp" [6], "Pixie Crunch" [7], and "GoldRush" [8]. In addition to the scab-resistant apple cultivars released by the PRI breeding program, several cultivars have also been released by breeding programs at Cornell University in NY, by Agriculture Canada, and by the National Institute of Agronomic Research in Angers, France, and Consorzio Italiano Vivaisti in Italy, and Breeding Initiative Niederelbe in Germany [9].Despite the introduction of several apple scab-resis...